#include <stdio.h>
#include <stdlib.h>

_CRTIMP extern char **_environ;

int main(int argc,const char *argv[]){
    if (_putenv_s("MY_NEW_VAR","new_value") != 0){
        /* Handle error */
    }
    if (_environ != NULL){
        for (size_t i = 0;_environ[i] != NULL; ++i){
            puts(_environ[i]);
        }
    }
    return 0;
}